How I do it over the network:
You need to create a "Scans" folder on your sp.
Share it.
Access your printer through your browser via it's ip address: 192.168.x.x
Go to the scans section
Enter the share path which would be something like \\Surfacepronames\scans
Then back on the physical printer it self under scan>scan to network folder, you should see it there

Via usb:

Once plugged in via usb just search in Cortana for scan and open windows fax and scan and hit new scan